In order to manage ever increasing traffic numbers, special lanes are introduced that allow only traffic with more than a certain number of occupants inside a vehicle. These managed lanes include carpool, diamond, or HOV lanes that are intended to reduce the total number of cars (for a given number of people) on the highway and thus to speed up travel. The overall benefits are obvious in multiple areas and the managed lanes reduce lost time, reduce fuel consumption and decrease pollution. Managed lanes, such as HOV lanes, are typically the left most lanes of a highway and are often denoted by diamond markings on the pavement within the lanes and/or signage.
In order to be effective, the adherence to the occupancy numbers has to be enforced. Since managed lanes generally give a clear advantage in terms of travel time, people are tempted to cheat the system and use the lane even if the vehicle does not carry the sufficient number of occupants (or is otherwise ineligible). This tendency to cheat sometimes also includes efforts to avoid detection, including the use of dummies or mannequins to simulate a second passenger.
To enforce the rules of managed lanes, current practice requires dispatching law enforcement officers at the side of HOV/HOT lanes to visually examine passing vehicles. This method is expensive, difficult, and ultimately ineffective as few violators are actually caught and ticketed. An alternate method of monitoring managed lanes is image-based automatic enforcement which requires identification and classification of image features (e.g., faces, seats, seat belts, etc.) behind a windshield that are visible to the camera to distinguish a driver+passenger configuration vs. a driver only configuration. This method is highly dependent upon camera placement and timing to obtain a clear image of the interior of a vehicle.
The clear incentive to cheat establishes the need that a police officer (or other authorized person) can easily verify if there is a sufficient number of people in the car. In order to do this effectively, the police officer has to be able to make the determination while traffic is moving at highway speed and false positives should be kept to a minimum. In some currently employed systems, an officer gets a visual representation of the car and has to use his/her display to decide. An example of such visual representations taken using conventional equipment (near-infrared (NIR) camera illumination camera) is illustrated in images 10 of FIG. 1.
From FIG. 1, it can be appreciated that often the actual camera data is not a good source for making any decision, since the total dynamic range of the image—in general—is way too high to be directly useful.